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LATI VOR/DME Approach RWY 18


bpcw001

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Hi,

I recently flew the RWY 18 VOR/DME approach into LATI as follows:

Vectored till VOLBI, then direct-to VOLBI with radial-in 352. Intercept point was calculated and radial was correctly intercepted, NAV mode on FMA, altitude 4000ft already.

VOLBI is the IF. From there, there is a step-down to 3000ft to the FAF.

So, approaching VOLBI at 4000ft on R352 inbound with NAV, approach mode enabled in the MCDU, FMA: SPEED|ALT|NAV, I switched to TRACK/FPA (bringing up the V/DEV scale) and armed the approach (APP button) upon which I get the respective blue annunciations on the FMA.

However, upon reaching VOLBI, the aircraft does not start to descend. The aircraft stays in ALT/NAV mode at 4000ft although the V/DEV indicator shows that a descent should be made.

So, I manually intervened to descend via FPA to the FAF, upon which I re-engaged APP mode and then the aircraft followed the V/DEV vertical path with FINAL APP on the FMA.


So, my question: Is the FINAL APP mode supposed to work only starting from the FAF, but not from the IF? From which point is it supposed to kick in?

I have no problem flying this laterally managed and vertically selected FPA|NAV or both laterally/vertically selected FPA|TRACK, but I would like to know what I did wrong here.

Thanks

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OK, I did it again and it is consistently so that the vertical navigation of the APP mode starts at the FAF only. Doing some more research this seems to be OK and according to how that works in the real world (anyone with knowledge care to confirm?)

However, before reaching the FAF with the whole thing switching directly into FINAL APP mode on the FMA, I don't get an ALT green (FINAL blue armed) and APP NAV green although I am perfectly on the lateral track for the approach and the lateral "capture" should be there even before reaching the FAF.

Not modeled?

 

Other than that, I am quite happy with the NPA capabilites of this bird :-)

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my research / experience confirms yours about APP mode .... but I'm not a real airbus driver !

one thing i understand about "capture" annunciations is that they are armed correctly if in both managed modes but not if in one or both selected modes.

but as i mentioned, i;m not sure that's real nor do i know if it is modelled whichever way.

cheers

ps you might enjoy reading the attached from airbus

 

AirbusSafetyLib_-FLT_OPS-GEN-SEQ02.pdf

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Hi uadriver,

thanks for your input and the link to the airbus doc. I had stumbled across that document on the internet before.

As for the "capture" annunciations, there should not be much as soon as you're selected. Typically, you have:

- Laterally selected, vertically selected -> only FPA and TRK on the FMA, no "capture" of anything since nothing is armed

- Laterally managed, vertically selected -> FPA, and for lateral mode if you're not already NAV: HDG/TRK with a blue NAV armed for a typical intercept via radial-in to a fix

- Fully managed: we should see:  ALT (green) FINAL (blue) and APP NAV (green) as soon as laterally "captured" but not vertically yet, switching to green "FINAL APP" across both lateral and vertical parts of the FMA on V/DEV "capture".

As far as I can see, the only thing we're missing out here is that "laterally captured, vertically not yet" annunciation when in fully managed mode. It just stays all armed until both lateral and vertical capture is achieved, then immediately switching to "FINAL APP".

 

 

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  • Deputy Sheriffs

Hi bpcw001 and uadriver,

I finally had some time to look into this. More or less everything that you two have come up with is correct. At the moment the AS Airbus is modelled to fly an NPA fully managed approach starting at the FAF, in this case TRN95. Vertical interception from above this altitude (3000 in this case) is not modelled but under certain conditions possible in RL but not considered SOP by us. The dev decided to only model the 3000. 

There are two things missing in the NPA fully managed story for the AS Airbus. First there is no possibility to have APP NAV active and Final armed. You already came to this conclusion in the above post. I hope this will be rectified for the A330 and later on also for SP4. Second, there should be a blue descent arrow at the FAF or FAWP on the ND to indicate that the profile will start there and the AFS is using it for its calculations. I have not yet been able to convince the dev of this "missing feature" in the AS Airbus as documentation about it is rare and video and or pictures are not enough evidence to support my claim. But rest assured I am on it. ;)

Enjoy your fully managed approaches and please start them (vertically) at the FAF or FAWP for now.

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frank

thanks for your notes ....& what we hope to see modelled in the near term.

thanks also to you bpcw001 for starting the topic & contributing even further.

I guess soon we'll be asking if "the constant angle" descent using vnav(managed) from the IAF to final app after FAF can be modelled (fig #30 katmandu in the airbus study refers) for RNP approaches ... if such is now possible in the real.

cheers john

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21 hours ago, The Dude said:

 

 

 

Hi bpcw001 and uadriver,

 

 

 

 

I finally had some time to look into this. More or less everything that you two have come up with is correct. At the moment the AS Airbus is modelled to fly an NPA fully managed approach starting at the FAF, in this case TRN95. Vertical interception from above this altitude (3000 in this case) is not modelled but under certain conditions possible in RL but not considered SOP by us. The dev decided to only model the 3000. 

 

 

 

 

There are two things missing in the NPA fully managed story for the AS Airbus. First there is no possibility to have APP NAV active and Final armed. You already came to this conclusion in the above post. I hope this will be rectified for the A330 and later on also for SP4. Second, there should be a blue descent arrow at the FAF or FAWP on the ND to indicate that the profile will start there and the AFS is using it for its calculations. I have not yet been able to convince the dev of this "missing feature" in the AS Airbus as documentation about it is rare and video and or pictures are not enough evidence to support my claim. But rest assured I am on it. ;)

 

 

 

Enjoy your fully managed approaches and please start them (vertically) at the FAF or FAWP for now.

 

 

 

Hey, thanks a lot for chiming in here! Always great to hear from you real-world pilots!

And thanks for trying to convince the devs to add what's missing (how could they refuse to heed real-world pilot input? :D)

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